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Old August 20th, 2008, 09:33 PM   #1
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T-Power vs. 48V phantom power

Can you please state what, if any, differences there are, either in terms of performance and/or functionality between T-power and 48V power? Are there situations that arise where the T-power version of a mic (as in Sennheiser 416 or 816) would be preferable to the P48 version?
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Old August 20th, 2008, 11:13 PM   #2
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there's absolutely no difference of quality between 12v and 48v. It used to be that 12v powering was a standard, it has nothing to do with european models. Overtime 48v became a standard. you can use a 416T and a 416 p48 and they sound exactly the same. If you got a recorder that only accepts 12v (like the older nagras) then you have no choice but to use 12v.
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Old August 20th, 2008, 11:20 PM   #3
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Also T power and Phantom power (either 48V or 12V) are different in the way they put the voltage on the line. I always get confused about the details because I don't use T power but the fundamental difference between T power and Phantom power is not so much about the voltages as it is about how the voltage gets delivered to the mic, ie which wires in the cable actually carry the current.
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Old August 21st, 2008, 04:52 AM   #4
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In a nutshell mic power is aq DC voltage sent to the mic on the same cable that the audio comes back on. A balanced line has signal hot, signal cold, and a ground conductors. T-power puts the 12v DC across the signal hot and signal cold conductor, ground is neutral. Phantom puts DC across both of the 2 signal conductors together and the ground conductor.

If you connect a dynamic or a ribbon mic to a cable carrying T-power, current will flow through the mic capsule, potentially damaging the dynamic mic and almost certainly destroying the ribbon mic. But with phantom, since signal hot and signal cold are at the same positive DC potential, no current flows and the chance of damage is much less. The relative safety from accident mic damage is one of the key reasons phantom has largely replaced T-power.
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Old August 21st, 2008, 05:09 AM   #5
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Dear Steve,

Nice post, as always!
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Old August 21st, 2008, 07:35 AM   #6
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Quote:
Originally Posted by Dan Goulder View Post
Can you please state what, if any, differences there are, either in terms of performance and/or functionality between T-power and 48V power? Are there situations that arise where the T-power version of a mic (as in Sennheiser 416 or 816) would be preferable to the P48 version?
Thanks.
Dan the differences between T Power and Phantom Power relate to the voltage and configuration on the pins provided to the mike as others have stated. IMHO Phantom is preferable as it interacts better or less with non phantom signals from other non phantom mics. T power can change/effect the sound quality of mics which are not using T Power in ways which not everyone will easily diagnose even if it doesn't actually damage the mic. If used properly T power works very reliably but it is not supplied by many new pieces of gear so I would choose Phantom for any new purchases.
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Old August 22nd, 2008, 11:58 AM   #7
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I think I read somewhere that T power is advantageous for very long cable runs because it reduces the likelihood of interference.
Does anyone know if this is true?
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Old August 22nd, 2008, 04:35 PM   #8
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Quote:
Originally Posted by Richard Gooderick View Post
I think I read somewhere that T power is advantageous for very long cable runs because it reduces the likelihood of interference.
Does anyone know if this is true?
I may be wrong but I'm not aware of any principle of physics that would lead to such behaviour.
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Old August 22nd, 2008, 10:26 PM   #9
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Quote:
Originally Posted by Richard Gooderick View Post
I think I read somewhere that T power is advantageous for very long cable runs because it reduces the likelihood of interference.
Does anyone know if this is true?
It's possible that what you read was referring to use of balanced audio generally, for which this is true.
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Old August 23rd, 2008, 01:41 AM   #10
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T vs P

What may be the cause of this rumour is the reliance of Phantom powering on the screen as one of its conductors. Maybe in the past someone's cables had frayed screening and Phantom powering got blamed for the breakdown! I guess another advantage of Phantom is that you can tolerate another cable-soldering mistake, reverse phasing, whereas T powering will present reversed polarity to the mic.
Another point to consider is introducing in-line attenuators. T powering certainly will NOT like it, as the H circuit in most attenuators will short it out. Now I'm not at all certain about the effect of inserting an in-line attenuator with Phantom (all my gear is T powered, so I haven't (rashly) experimented). The bridge between the signal conductors will not have an effect on the powering, but the resistors on the other legs may do something nasty. Any answers, anyone?
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Old August 23rd, 2008, 02:34 AM   #11
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Quote:
Originally Posted by Phil Bambridge View Post
It's possible that what you read was referring to use of balanced audio generally, for which this is true.
I understand that audio is better when it's balanced (although I'm so untechnical that it makes my brain hurt when I try to understand why).
Actually now that I think about it more I think that I was told that T power is more reliable for long cable runs ie of hundreds of feet. I don't think that I read it.
But as Nick says, it is probably a rumour.
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Old August 23rd, 2008, 05:17 AM   #12
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Balanced vs Unbalanced

Now I'd welcome my comments receiving expanding and clarification posts, but for the non-technical perhaps a good way to visualise the difference between balanced and unbalanced is to look at the cable itself. Unbalanced has one core surrounded by a screen, so it doesn't take Sherlock Holmes to deduce that the screen has to take one leg of the signal. Balanced cable has two cores, which take the signal from the microphone, surrounded by a screen which is usually connected to the chassis of the mixer (or camera or whatever) at the receiving end and the body of the mic at the other. So the signal cores are protected (up to a point) from magnetic fields by this screen all the way along the path. Any similar magnetic fields (and laying your mic cable next to a mains cable will do very well for inducing hum: if you have to cross one, make sure it is at right angles) will be inducing their unwelcome effects into the screen of an unbalanced cable which is also carrying the signal. And that can cause much gnashing of teeth.

Perversely, sometimes lifting the screen will get rid of hum, when two bits of equipment (one usually mains powered) are connected by a balanced cable....but that is another question.
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Old August 23rd, 2008, 06:14 AM   #13
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Thanks Nick
A very helpful explanation.
Returning to the theme of this thread. It seems that there is no difference between P and T except that T might _possibly_ screw up your mics.
Another thing that I have noticed is that T powered versions of the same mic eg sennheiser 416, seem to go less than the P powered equivalent in the secondhand market.
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Old August 23rd, 2008, 07:42 AM   #14
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P vs T in cost

If my memories of the circuits of T and P powering doesn't betray me, at the microphone end you need a transformer with a centre tap to separate the Phantom power from the audio, whereas with T powering just a network of capacitors does it. It could be just component cost.
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Old August 23rd, 2008, 08:05 AM   #15
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In my opinion, the T-Powered microphones are less expensive since that are usually much older.

The generally accepted standard today, in my opinion, is phantom power.

The T-Powered mics still work and work well, but there is less equipment, such as mixers, that support T-Power.

For example, Canon's XL H1, XL H1s, XL H1a, XH A1, XH G1, etc all support phantom powered mics but not T-powered mics.

You will need a proper mixer (or separate T-Power power supply) to power a T-Powered mic.

What worries me the most, is that if you have T-Powered mics, then you will need to set you mixer to provide T-power. Then, if you accidently plug someting in that is not T-Powered, such as wireless mic receiver, you take the risk of damaging it.

It is not good practice to plug in a wireless mic receiver into a mixer with phantom power activated, but with Sennheiser G2's it will generally not damage it.

Personally, I have made the above mistake, and then corrected it fairly quickly.

I have never made the mistake with the T-Power option on, since I have been very carefull to never set the T-Power option on, on my mixer. Frankly, I do not know if it would damage the G2, but I do not want to test it.

So, in my opinion, the T-Powered mics are less expensive because the phantom powered mics are more popular since they are supported by more devices.
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